Sexually Transmitted Shigella: What Gay & Bisexual Men Need to Know

Sexually Transmitted Shigella: What Gay and Bisexual Men Need to Know

Diarrhoea isn't usually the first thing that comes to mind when people think about sexually transmitted infections (STIs). But a growing body of research shows that Shigella — a bacterium best known for causing infectious diarrhoea — is now spreading through sexual contact, particularly within sexual networks of gay, bisexual, and other men who have sex with men (MSM). Some strains are becoming increasingly difficult to treat because of rising antimicrobial resistance.

If you're sexually active, especially with multiple partners, it's worth understanding what sexually transmitted Shigella is, how it spreads, and why testing matters more than ever.

What Is Shigella?

Shigella is a highly contagious bacterium that causes shigellosis, an intestinal infection. It typically leads to:

• Diarrhoea, which can be bloody or prolonged
• Stomach cramps
• Fever
• Nausea and vomiting
• Dehydration in more severe cases

Shigella has traditionally been associated with contaminated food and water, poor sanitation, overseas travel, and outbreaks in childcare settings. It remains one of the leading causes of diarrhoeal illness in children in low- and middle-income countries.

Although Shigella has long been capable of spreading through sexual contact, sexual transmission has become an increasingly important driver of outbreaks in some communities over the past two decades.

The Research: Sexually Transmitted Shigella Is Outpacing Other Forms

A study led by the University of Cambridge, in collaboration with the UK Health Security Agency (UKHSA) and published in The Lancet Infectious Diseases, offers the clearest picture yet of how this shift has happened.

Recent genomic research has helped explain why sexually transmitted Shigella is becoming an increasing public health concern. Researchers analysed 3,514 Shigella samples collected across the UK between 2004 and 2020, from patients over the age of 16. Genomic sequencing of the samples revealed:

• Around a third of cases (34%) were linked to men who have sex with men
• Another third (36%) were domestic cases not linked to MSM transmission
• The remaining third (30%) were travel-related cases brought into the UK from abroad

Between 2015 and 2020, sexually transmitted strains of Shigella grew roughly 15% faster year-on-year than strains linked to travel, contaminated food, or nursery outbreaks. Sexually transmitted strains also spread more than twice as fast geographically across the country compared with other forms of the infection.

Perhaps most concerning: more than 70% of sexually transmitted Shigella strains were resistant to at least one clinically important antibiotic by the end of the study period, compared with 49% of travel-related strains and 40% of non-sexually transmitted cases.

Professor Kate Baker, senior author of the study from Cambridge's Department of Genetics, noted that many men who have sex with men remain unaware of the growing risk and that sexual transmission is now a sustained part of how Shigella circulates in the UK — serious enough to be treated as a distinct public health threat.

UKHSA data backs this up: laboratory-confirmed diagnoses of sexually acquired Shigella rose sharply through 2025, reaching 2,560 recorded cases—up from 2,052 in 2023.

Why Is Shigella Spreading Sexually?

Shigella is transmitted via the faecal-oral route. Sexually, this usually happens through direct or indirect contact between the mouth and the anus (oral-anal sex) or contact with objects, fingers, or surfaces that have come into contact with faecal matter. Because Shigella is extremely infectious — it takes as few as 10 bacterial organisms to cause illness, compared with over 1,000 for Salmonella — even minimal exposure during sex can be enough to transmit it.

Researchers believe the sharp rise in cases since around 2010 is linked to several factors, including:

• Increased use of geospatial dating and hook-up apps that connect people to more sexual partners
• Group sex and sexual networks with multiple concurrent partners
• Chemsex (drug use during sex), which can increase risk-taking behaviour
• Two species in particular, Shigella flexneri and Shigella sonnei, have been the main drivers of these outbreaks, cycling through the community as new antibiotic-resistant strains emerge and outcompete older ones

Why Antibiotic Resistance Is a Serious Concern

Most Shigella infections are self-limiting, meaning the body can clear them without medication. However, antibiotics are often needed for more severe or prolonged cases and to reduce the risk of passing the infection on to others.

The problem is that sexually transmitted strains of Shigella have been evolving resistance to the antibiotics doctors rely on far faster than other strains — including first-line treatments like ciprofloxacin and second-line options like azithromycin. Some extensively drug-resistant (XDR) strains have already been identified, leaving very few effective treatment options. This is why public health experts are urging earlier testing, prompt treatment, and greater awareness, rather than waiting for symptoms to escalate.

Who Is at Risk?

While anyone can contract Shigella through contaminated food or poor hygiene, sexually transmitted Shigella is currently concentrated in sexual networks of men who have sex with men, particularly in urban areas. It's important to note that this isn't about identity — it's about specific sexual practices and networks, and it can affect anyone engaging in oral-anal contact or having multiple sexual partners, regardless of orientation.

If you fall into any of the following categories, it's worth paying closer attention:

• You have multiple sexual partners or meet partners through dating/hook-up apps
• You engage in oral-anal contact
• You participate in group sex or chemsex
• You've had unexplained, prolonged, or bloody diarrhoea after sexual activity
• You've recently been diagnosed with another STI (co-infections are common)

Symptoms to Watch For

Shigella symptoms typically appear 1 to 3 days after exposure and can include:

• Watery or bloody diarrhoea
• Frequent, urgent bowel movements
• Abdominal cramping
• Fever
• Nausea or vomiting
• Fatigue and dehydration

Because these symptoms overlap with other gastrointestinal and sexually transmitted infections, self-diagnosis isn't reliable. Lab testing is the only way to confirm Shigella and rule out other infections that may be present alongside it.

Getting Tested: Why It's Worth Checking More Than One Thing

Shigella is diagnosed through a stool test (stool culture or stool PCR), which is different from the swab or urine tests used for infections like chlamydia, gonorrhoea, HIV, or syphilis. Because sexually transmitted Shigella often shows up alongside other STIs — and because its symptoms can be mistaken for other gut infections — it's worth getting a full picture rather than testing for just one thing.

At PULSE Clinic, this means combining the right test for your symptoms:

• If you have gastrointestinal symptoms such as prolonged or bloody diarrhoea, cramping, or fever, ask about a stool test for Shigella and related gut infections.
• For a broader sexual health check covering other common STIs, PULSE Clinic's PCR31 test offers a comprehensive, highly sensitive PCR panel in a single visit.

Our clinical team can advise on which combination is right for you based on your symptoms and exposure — you don't need to figure this out on your own.

If you do test positive, our clinicians can guide appropriate antibiotic treatment based on current resistance patterns and arrange follow-up testing to confirm the infection has cleared before you resume sexual activity. If needed, we can also support confidential partner notification, so anyone you may have exposed can get tested too.

Comprehensive STD Testing with PCR31

A comprehensive STD test — sometimes called a full STD screening or STD panel — checks for multiple sexually transmitted infections in a single visit, rather than testing for just one. The exact infections covered vary by clinic and laboratory, but a good comprehensive screening should cover the most common and clinically significant bacterial, viral, and parasitic STIs.

PULSE Clinic's PCR31 test uses multiplex PCR technology to detect 31 different organisms from a single urine sample or swab – one test, 31 microbes, and multiple body areas, all in one visit. It's a fast, highly sensitive way to check your overall sexual health status alongside any symptom-specific testing your clinician recommends.

Because PCR31 is urine- and swab-based, it's designed for genital, oral, and blood-borne STIs rather than gut infections like Shigella — which is why a separate stool test is used when gastrointestinal symptoms are present. Our team can arrange both in the same visit if needed.

One test. 31 microbes. Multiple body areas.

PCR31 Test – STD Screening Promotion at PULSE Clinic Thailand

• Prices are in Thai baht.
• Online results will be available at the PULSE Online Portal (POP) and the E-Doc mobile application
• For same-day result testing, the sample must be taken at the clinic before noon (12:30 PM)
• Same-day and next-day results are only available at the Bangkok, Pattaya, and Phuket branches

Book Assessment and Treatment with us

Contact us at info.bkk@pulse-clinic.com or chat on your preferred platform:

Prevention Tips

While no method is 100% foolproof, you can reduce your risk by:

• Using barriers (such as dental dams or condoms) during oral-anal contact
• Washing hands, genitals, and sex toys thoroughly before and after sex
• Avoiding sex if you or a partner has active diarrhoea or gastrointestinal symptoms
• Getting tested regularly if you have multiple partners, even without symptoms
• Talking openly with partners about testing and symptoms
• Asking about Hepatitis A vaccination, since Hepatitis A spreads the same way as sexually transmitted Shigella and is specifically recommended for sexually active gay and bisexual men — speak to our clinical team about whether it's right for you
• Avoid sexual activity until your diarrhoea has completely resolved and your clinician advises it's safe to resume sex

Frequently Asked Questions

Is Shigella officially classified as an STI?

Shigella is primarily known as a foodborne bacterial infection, but health authorities, including the UKHSA, now recognise sexual contact — particularly oral-anal contact — as an established route of transmission, especially within some MSM sexual networks.

Can Shigella be cured?

Many cases resolve on their own with rest and hydration. However, some strains now show resistance to common antibiotics, so it's important to get tested and follow a clinician's guidance rather than self-treating.

How soon after exposure should I get tested?

If you develop symptoms such as diarrhoea, cramping, or fever within a few days of sexual activity, it's best to get tested promptly. Even without symptoms, regular testing is recommended if you have multiple partners.

Does the PCR31 test check for Shigella?

PCR31 is a comprehensive panel covering a wide range of sexually transmitted infections. Shigella is typically diagnosed separately through a stool test, since it's a gut infection rather than a genital or blood-borne one. If you have diarrhoea-type symptoms, mention this to our clinical team so they can arrange the correct test alongside or instead of PCR31.

Can I get vaccinated against infections linked to sexual activity?

Yes – Hepatitis A vaccination is recommended for sexually active gay and bisexual men, as it spreads through the same routes as sexually transmitted Shigella. Ask our clinical team whether this, or other vaccinations, are appropriate for you.

Is testing confidential?

Yes. PULSE Clinic provides confidential, judgement-free sexual health testing and counselling in a supportive environment.

Does DoxyPEP prevent Shigella?

No. DoxyPEP is used to reduce the risk of some bacterial STIs, such as syphilis and chlamydia, but it is not recommended for preventing Shigella. In fact, unnecessary antibiotic use may contribute to antimicrobial resistance. If you're considering DoxyPEP, speak with your clinician about whether it's appropriate for you.

Take Charge of Your Sexual Health

Sexually transmitted Shigella is a reminder that STI risk isn't limited to the infections most people already know about. As antibiotic resistance grows, early detection is one of the most effective tools available.

If you think you may have been exposed, are experiencing symptoms, or want a comprehensive sexual health check-up, book a consultation at PULSE Clinic today.

Our team will guide you to the right test for your situation — whether that's a stool test for Shigella, the PCR31 panel for a broader STI screen, or both — and support you with treatment, follow-up, and vaccination advice where relevant, delivered confidentially and without judgement.

Book Assessment and Treatment with us

Contact us at info.bkk@pulse-clinic.com or chat on your preferred platform:

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. If you are experiencing symptoms, please consult a qualified healthcare provider or visit PULSE Clinic for testing and guidance.

Sources: University of Cambridge; UK Health Security Agency (UKHSA); The Lancet Infectious Diseases.